Quantitative measurement of cellulosic filler dispersion in thermoplastic composites

An image analysis technique was employed to quantitatively measure cellulosic filler dispersion in linear low density polyethylene (LLDPE) polymer for the assessment of a high intensity shear compounding process in manufacturing wood-fiber thermoplastic composites. Graphic images of samples obtained with a confocal microscope were analyzed by assigning different colors to the pixels which had different laser intensities depending on different reflecting behavior. A mixing index based on the variance ratio of sample mixture to that of ideal mixture was successfully applied for the quantification of cellulosic filler dispersion in LLDPE resin. The quantified filler dispersion was not directly related to the mechanical properties. However, the addition of dispersing agent improved filler dispersion and, in some cases, increased the strength and modulus of composites.